Fenton 1977.

Methods	Quasi‐randomised trial, 2 arms with individual randomisation.
Participants	154 pregnant women with less than 14 weeks of gestation, and who had not received or were receiving treatment for a blood disorder at clinic in Cardiff, United Kingdom.
Interventions	Participants were divided into 2 groups according to the day in which they attended the clinic in Cardiff: group 1 received 60 mg of elemental iron (as ferrous sulphate) daily and group 2 received no iron supplement. Setting and health worker cadre: the intervention was performed by physicians at the Antenatal Clinic of the Welsh National School of Medicine at the University Hospital of Wales, Cardiff, United Kingdom.
Outcomes	Hb concentration, MCV, serum ferritin, serum iron and total iron binding capacity were measured at 10‐14 weeks and at term.
Notes	The data in the paper are presented with no SD values. No data can be extracted from the publication for this review. Gestational age at start of supplementation: early gestational age. Anaemic status at start of supplementation: mixed/unspecified anaemia status. Daily iron dose: higher daily dose (60 mg or elemental iron). Iron release formulation: normal release preparation/not specified. Iron compound: ferrous sulphate. Malaria setting: non‐malarial setting. As of 2011: Malaria: no risk.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	High risk	By day of clinic attendance.
Allocation concealment (selection bias)	High risk	By day of clinic attendance.
Blinding of participants and personnel (performance bias) All outcomes	High risk	No blinding.
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	Laboratory outcomes but women were treated for anaemia and this may have affected results for this outcome.
Incomplete outcome data (attrition bias) All outcomes	Low risk	All women appear to be accounted for in the analyses; separate figures are provided for women in the control arm who received supplements.
Selective reporting (reporting bias)	Unclear risk	There is insufficient information to permit judgement.
Other bias	Unclear risk	No other bias apparent.